There was a group of collective nuns standing outside of the Everytown Bank; they were rattling their tins and rosaries in a sort of beatbox style.
I don’t know what the collective noun is for a group of collective nuns; but, I’m sure that it’s something like a ‘habitual’ of collective nuns, or the like.
#JustSaying
Graeme Sandford 
Nuns Convent, Murmur, Flap, Pray, Superfluity
I do so like the idea of the sound of a superfluity of Nuns …
It has a certain appeal…
G:)